Molly Menefee

Question 1

Explain actin treadmilling. What region of the growth cone does this occur? How does this cause growth and retraction?

Answer 1

Actin treadmilling is the constant cycling (in a retrograde fashion) of actin monomers in a filament. Polymerization occurs in the leading edge (peripheral domain) and depolymerization occurs in the transition zone. A steady state is achieved when the rate of assembly and the rate of depolymerization are equal. When the filament disassembles at a faster rate than it polymerizes it retracts. Growth is established when polymerization rate is faster than depolymerization rate.

Question 2

Myosin-II plays a crucial role in retrograde flow of actin in the growth cone.

Answer 2

F

Question 3

Stabilization of actin filaments by jasplakinolide inhibits network turnover and leads to growth cone retraction.

Answer 3

T

Question 4

Jasplakinolide stabilizes actin filaments and was shown to cause what structural changes in A. californica bag cell neurons?

Answer 4

a. Central domain contracts and compresses

Question 5

Some repulsive or attractive axonal guidance cues promote actin turnover. What is a possible mechanisms for a turnover signaling pathway that affects growth cone motility via an actin mechanism?

Answer 5

b. Modulate rate of actin polymerization in leading edge by changing actin monomer concentration and /or barbed end density